This invention relates to an improved liquid filtering apparatus of the separable plate type and more particularly, it relates to such a filtering apparatus in combination with an improved mechanism for supplying fresh filter media to, and removing used filter media from, the filtering apparatus.
In U.S. Pat. No. 3,608,734, a filtering apparatus is described wherein a series of horizontal plates are arranged in a stacked arrangement to form a series of inlet chambers for dirty liquid to be filtered. The plates are separable to an open position to allow placement of a sheet of filter media between them and when closed, they are sealed against the media around their edges to form an inlet chamber for each plate on one side of the media and, under a suitable grill, a collection chamber for clean, filtered liquid on the opposite side of the media. The inlet chambers are each connected to an inlet conduit for dirty liquid and the collection chambers are connected in parallel to a common conduit for clean filtrate.
In the aforesaid patent, filter media in the form of filter paper supplied from rolls located adjacent one side of the filter plates, is pulled between the plates by a media pulling apparatus adjacent the other side of the plates. The pulling apparatus includes a mechanism for inserting pins into the filter media to move it for a sufficient distance so that used filter media is completely removed from between each adjacent pair of separated filter plates and is replaced by fresh media before the plates are again closed. Heretofore, such an arrangement was particularly useful where additional filter media, such as diatomaceous earth, was added to, and allowed to build up, to form a cake on the filter paper media during a typical filtering cycle. As an alternative to the aforesaid patented pin-type media moving mechanism, it was suggested that the paper type filter media be pulled, using a crown roller in combination with a pinch roller, connected to a driving mechanism. Although such an expedient was operable to a limited degree with plain paper type filter media, it was not at all satisfactory for application where additional filter media was used to form a filter cake on the paper media or where an excessive buildup of filtered-out material occurred on the paper media. With such a thick layer of filter media, the filter cake or accumulated dirt, could not be passed between the crown roller and its pinch roll. Thus, the pinch roll could not hold the filter media against the crown roll so as to be driven satisfactorily and in many instances the media would track off to one side of the crown roll and prevent proper sealing of the media by the closing plates. Such erratic operation required continuous surveillance and manual adjustments and thus prevented the filter from being operated automatically and unattended for long periods of time.
A further problem with such plate type filters involving the filter media arose with respect to the necessity of providing a readily accessible paper supply, namely, the required rolls of paper media for the various pairs of filter plates. Not only was it necessary to provide means for quickly and easily replacing large paper rolls, but it was equally essential to provide a paper roll support means that would enable the paper to stay properly aligned relative to the plates during a media changing cycle. The present invention solves these and other problems associated with the filter media supply and removal system for plate type filters.